I've had this happen on a number of Contours that I've had. The problem is most likly pressure build up from running the tank dry. Make sure your car is on level ground before you try to add fuel. If you are on a slope the vapor will be trapped and will not allow fuel in. Even the slightest grade (with rear down hill) may not allow fuel in. Once your car is level you should be able to slowly pour it in. If not you can try one of two things....once the fuel filler neck is full of fuel(but not entering the tank) you can turn the key to the run position. This will start the fuel pump for a few seconds and should drop the pressure in the tank. If this doesn't work then you will need to remove the rear seat bottom(to access the fuel pump)and remove the pump just enough to break the seal and allow the vapor to release. I've only had to do that one once before.
Here is what happens...the fuel tank is a sealed pressurized system so when you run out of fuel it creates a vaccumm that closes the vapor valve for the filler neck. On these cars it tends to stick when that happens. If you've noticed, the filler neck is actually two hoses. One is the fuel filler and the other is the vent. With out the vent hose working correctly fuel will not be able to enter the tank. The air that is be displaced by the fuel needs to go some where and if things are working correctly it should flow out the vent hose.
